１）求等差數列１７，１４，１１，．．．的第ｎ項
２）a,b,c,d,e組成一等差數列。若b+e=26 及a+c+d=29, 求公差。
～～～數學題～～～
2007-06-10 1:54 am
回答 (4)
2007-06-11 1:19 am
✔ 最佳答案
1)第ｎ項=17-3(n-1)=20-3n2)let 公差=f
b+e=26 -------2a+5f=26
a+c+d=29---------3a+5f=29
a=3
f=4
參考: me
2007-06-10 2:09 am
1) first term = 17, common difference = -3
T (n) = 17 - 3(n-1) = 21 - 3n
2) 設公差為y,
b+e = 26
(a+y) + (a+4y) = 26
2a+5y = 26 ..........(i)
a+c+d = 29, i.e. a+(a+2y)+(a+3y) = 29
3a+5y = 29 ..........(ii)
By solving (i), (ii), we have y = 4
T (n) = 17 - 3(n-1) = 21 - 3n
2) 設公差為y,
b+e = 26
(a+y) + (a+4y) = 26
2a+5y = 26 ..........(i)
a+c+d = 29, i.e. a+(a+2y)+(a+3y) = 29
3a+5y = 29 ..........(ii)
By solving (i), (ii), we have y = 4
參考: me
2007-06-10 2:00 am
１）求等差數列１７，１４，１１，．．．的第ｎ項
n=17+(n-1)(3)
２）a,b,c,d,e組成一等差數列。若b+e=26 及a+c+d=29, 求公差。
公差=29-26
=3
n=17+(n-1)(3)
２）a,b,c,d,e組成一等差數列。若b+e=26 及a+c+d=29, 求公差。
公差=29-26
=3
參考: me
2007-06-10 1:58 am
n=17+(n-1)(3)
公差=29-26
=3
公差=29-26
=3
收錄日期: 2021-04-13 00:50:20
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